Separate Accounts (Separate Account Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 117,293,384	$ 114,051,246
U.S. Treasury securities and obligations of U.S. government authorities and agencies
Fair Value, Separate Account Investment [Line Items]
Separate account assets	4,217	2,510
U.S. corporate securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	11,148	8,702
Foreign corporate securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	2,233	1,420
Mortgage-backed securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	649	276
Equity
Fair Value, Separate Account Investment [Line Items]
Separate account assets	68,363,666	67,144,660
Fixed Income
Fair Value, Separate Account Investment [Line Items]
Separate account assets	39,528,749	38,109,374
Other
Fair Value, Separate Account Investment [Line Items]
Separate account assets	3,852,446	3,441,016
Equity securities
Fair Value, Separate Account Investment [Line Items]
Separate account assets	61,027	49,260
Other invested assets
Fair Value, Separate Account Investment [Line Items]
Separate account assets	5,453,782	5,262,178
Short-term investments
Fair Value, Separate Account Investment [Line Items]
Separate account assets	4,861	1,237
Cash and cash equivalents
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 10,606	$ 30,613